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Fabrication of high-density cantilever arrays and through-wafer interconnects
Processes to fabricate dense, dry released microstructures with electrical connections on the opposite side of the wafer are described. A 10 x 10 array of silicon and polysilicon cantilevers with high packing density (5 tips/mm<sup>2</sup>) and high uniformity (<10 µm length variation across the wafer) are demonstrated. The cantilever release process uses a deep SF<sub>6</sub>/C<sub>4</sub>F<sub>8</sub>, plasma etch followed by a HBr plasma etch to accurately release cantilevers. A process for fabricating electrical contacts through the backside of the wafer is also described. Electrodeposited resist, conformal CVD metal deposition and deep SF<sub>6</sub>/C<sub>4</sub>F<sub>8</sub> plasma etching are used to make 30 µm/side square vias each of which has a resistance of 50 m(omega).
Date:
November 3, 1998
Creator:
A. Harley, J.; Abdollahi-Alibeik, S.; Chow, E. M.; Kenney, T. W.; McCarthy, A. M.; McVittie, J. P. et al.
Object Type:
Article
System:
The UNT Digital Library
The calculation of satellite line structures in highly stripped plasmas
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Recently developed high-resolution x-ray spectrographs have made it possible to measure satellite structures from various plasma sources with great detail. These lines are weak optically thin lines caused by the decay of dielectronic states and generally accompany the resonance lines of H-like and He-like ions. The Los Alamos atomic physics and kinetics codes provide a unique capability for calculating the position and intensities of such lines. These programs have been used to interpret such highly resolved spectral measurements from pulsed power devices and laser produced plasmas. Some of these experiments were performed at the LANL Bright Source and Trident laser facilities. The satellite structures are compared with calculations to diagnose temperatures and densities. The effect of non-thermal electron distributions of electrons on calculated spectra was also considered. Collaborations with Russian scientists have added tremendous value to this research die to their vast experience in x-ray spectroscopy.
Date:
November 1, 1998
Creator:
Abdallah, J. Jr.; Kilcrease, D. P.; Faenov, A. Ya. & Pikuz, T. A.
Object Type:
Report
System:
The UNT Digital Library
[Letter to Dr. D. Jack Davis from Julie Anne Abel - November 9, 1998]
A letter to Dr. D. Jack Davis from Julie Anne Abel regarding a grant check from the Getty Education Institute for the Arts to the North Texas Institute for Educators on the Visual Arts (NTIEVA).
Date:
November 9, 1998
Creator:
Abel, Julie A.
Object Type:
Letter
System:
The UNT Digital Library
[Letter from Julie Anne Abel to D. Jack Davis, November 17, 1998]
A letter from Julie Anne to D. Jack Davis about conforming the use of the Getty Education Institute for the Arts' National Specialty Program funds for the North Texas Institute for Educators on the Visual Arts.
Date:
November 17, 1998
Creator:
Abel, Julie Anne
Object Type:
Letter
System:
The UNT Digital Library
Reactive Ion Beam Etching of GaAs and Related Compounds in an Inductively Coupled Plasma of Cl(2)-Ar Mixture
Reactive ion beam etching (RD3E) of GaAs, GaP, AIGaAs and GaSb was performed in a Cl2-Ar mixture using an Inductively Coupled Plasma (ICP) source. `The etch rates and yields were strongly affected by ion energy and substrate temperature. The RJBE was dominated by ion-assisted etching at <600 eV and by physical sputtering beyond 600 eV. The temperature dependence of the etch rates revealed three different regimes, depending on the substrate temperature: 1) sputtering-etch limited, 2) products-resorption limited, and 3) mass-transfer limited regions. GaSb showed the overall highest etch rates, while GaAs and AIGaAs were etched at the same rates. The etched features showed extremely smooth morphologies with anisotropic sidewalls.
Date:
November 23, 1998
Creator:
Abernathy, C. R.; Hahn, Y. B.; Hays, D.; Lambers, E. S.; Lee, J. W.; Pearton, S. J. et al.
Object Type:
Article
System:
The UNT Digital Library
UV-Photoassisted Etching of GaN in KOH
The etch rate of GaN under W-assisted photoelectrochemical conditions in KOH solutions is found to be a strong function of illumination intensity, solution molarity, sample bias and material doping level. At low e-h pair generation rates, grain boundaries are selectively etched, while at higher illumination intensities etch rates for unintentionally doped (n - 3x 10^12Gcm-3) GaN are 2 1000 .min-l. The etching is diffusion limited under our conditions with an activation energy of - 0.8kCal.mol-1. The etched surfaces are rough, but retain their stoichiometry. PEC etching is found to selectively reveal grain boundaries in GaN under low light illumination conditions. At high lamp powers the rates increase with sample temperature and the application of bias to the PEC cell, while they go through a maximum with KOH solution molarity. The etching is diffusion-limited, producing rough surface morphologies that are suitable in a limited number of device fabrication steps. The surfaces however appear to remain relatively close to their stoichiometric composition.
Date:
November 12, 1998
Creator:
Abernathy, C.R.; Auh, K.H.; Cho, H.; Donovan, S.M.; Han, J.; Lambers, E.S. et al.
Object Type:
Article
System:
The UNT Digital Library
III-Nitride Dry Etching - Comparison of Inductively Coupled Plasma Chemistries
A systematic study of the etch characteristics of GaN, AlN and InN has been performed with boron halides- (BI{sub 3} and BBr{sub 3}) and interhalogen- (ICl and IBr) based Inductively Coupled Plasmas. Maximum etch selectivities of -100:1 were achieved for InN over both GaN and AlN in the BI{sub 3} mixtures due to the relatively high volatility of the InN etch products and the lower bond strength of InN. Maximum selectivies of- 14 for InN over GaN and >25 for InN over AlN were obtained with ICl and IBr chemistries. The etched surface morphologies of GaN in these four mixtures are similar or better than those of the control sample.
Date:
November 10, 1998
Creator:
Abernathy, C.R.; Cho, H.; Donovan, S.M.; Hahn, Y-B.; Han, J.; Hays, D.C. et al.
Object Type:
Article
System:
The UNT Digital Library
Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part I. GaAs, GaSb and AlGaAs
High density plasma etching of GaAs, GaSb and AIGaAs was performed in IC1/Ar and lBr/Ar chemistries using an Inductively Coupled Plasma (ICP) source. GaSb and AlGaAs showed maxima in their etch rates for both plasma chemistries as a function of interhalogen percentage, while GaAs showed increased etch rates with plasma composition in both chemistries. Etch rates of all materials increased substantially with increasing rf chuck power, but rapidly decreased with chamber pressure. Selectivities > 10 for GaAs and GaSb over AlGaAs were obtained in both chemistries. The etched surfaces of GaAs showed smooth morphology, which were somewhat better with IC1/Ar than with IBr/& discharge. Auger Electron Spectroscopy analysis revealed equi-rate of removal of group III and V components or the corresponding etch products, maintaining the stoichiometry of the etched surface.
Date:
November 23, 1998
Creator:
Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B. et al.
Object Type:
Article
System:
The UNT Digital Library
Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs
A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.
Date:
November 23, 1998
Creator:
Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B. et al.
Object Type:
Article
System:
The UNT Digital Library
Inductively Coupled Plasma and Electron Cyclotron Resonance Plasma Etching of InGaAlP Compound Semiconductor System
Current and future generations of sophisticated compound semiconductor devices require the ability for submicron scale patterning. The situation is being complicated since some of the new devices are based on a wider diversity of materials to be etched. Conventional IUE (Reactive Ion Etching) has been prevalent across the industry so far, but has limitations for materials with high bond strengths or multiple elements. IrI this paper, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma), for the etching of ternary compound semiconductors (InGaP, AIInP, AlGaP) which are employed for electronic devices like heterojunction bipolar transistors (HBTs) or high electron mobility transistors (HEMTs), and photonic devices such as light-emitting diodes (LEDs) and lasers. High density plasma sources, opeiating at lower pressure, are expected to meet target goals determined in terms of etch rate, surface morphology, surface stoichiometry, selectivity, etc. The etching mechanisms, which are described in this paper, can also be applied to other III-V (GaAs-based, InP-based) as well as III-Nitride since the InGaAIP system shares many of the same properties.
Date:
November 4, 1998
Creator:
Abernathy, C.R.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Pearton, S.J. & Shul, R.J.
Object Type:
Article
System:
The UNT Digital Library
Measurement of Neutron Total Cross Sections in Support of the APT Program
The authors have completed a new set of total cross section measurements of 37 samples spanning the periodic table. The authors employed the same technique as in a previous measurement, with refinements intended to allow measurements on separated isotopes, and with improved systematic error control. The goal of the new measurement was 1% statistical accuracy in 1% energy bins with systematic errors less than 1%. This was achieved for all but the smallest samples, for which the statistical accuracy was as large as 2% in 1% bins.
Date:
November 4, 1998
Creator:
Abfalterer, W. P.; Haight, R. C.; Morgan, G. L.; Bateman, F. B.; Dietrich, F. S. & Finlay, R. W.
Object Type:
Article
System:
The UNT Digital Library
Investigation of Deep Levels in GaInNas
This paper presents and discusses the first Deep-Level transient spectroscopy (DLTS) data obtained from measurements carried out on both Schottky barriers and homojunction devices of GaInNAs. The effect of N and In doping on the electrical properties of the GaNInAs devices, which results in structural defects and interface states, has been investigated. Moreover, the location and densities of deep levels related to the presence of N, In, and N+In are identified and correlated with the device performance. The data confirmed that the presence of N alone creates a high density of shallow hole traps related to the N atom and structural defects in the device. Doping by In, if present alone, also creates low-density deep traps (related to the In atom and structural defects) and extremely deep interface states. On the other hand, the co-presence of In and N eliminates both the interface states and levels related to structural defects. However, the device still has a high density of the shallow and deep traps that are responsible for the photocurrent loss in the GaNInAs device, together with the possible short diffusion length.
Date:
November 12, 1998
Creator:
Abulfotuh, F.; Balcioglu, A.; Friedman, D.; Geisz, J. & Kurtz, S.
Object Type:
Article
System:
The UNT Digital Library
Tropical Western Pacific site science mission plan. Semiannual project report, January--June 1998
The Department of Energy`s Atmospheric Radiation Measurement (ARM) program was created in 1989 as part of the US Global Change Research Program to improve the treatment of atmospheric radiative and cloud processes in computer models used to predict climate change. The overall goal of the ARM program is to develop and test parameterizations of important atmospheric processes, particularly cloud and radiative processes, for use in atmospheric models. This goal is being achieved through a combination of field measurements and modeling studies. Three primary locales were chosen for extensive field measurement facilities. These are the Southern Great Plains (SGP) of the United States, the Tropical Western Pacific (TWP), and the North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO). This Site Science Mission Plan [RPT(TWP)-010.000] describes the ARM program in the Tropical Western Pacific locale.
Date:
November 1, 1998
Creator:
Ackerman, T.; Mather, J.; Clements, W. & Barnes, F.
Object Type:
Report
System:
The UNT Digital Library
Design review report, 241-S-102 cover plate review
The design for the cover plate and lead plate for shielding on 241-S-102 was reviewed on 10/21/98. All Review Comment Record comments were resolved to the satisfaction of the reviewers. Additional comments were taken during the meeting and were also resolved. A design calculation for the Radiological Design Review Screening was presented as criteria for the use of 1 inch lead plate. The review concluded that the use of 2 inch steel plate and 1 inch lead plate provided the required safety function required by HNF-SD-WM-810-001, 5.3.2.20, Basis for Interim Operation. The design was approved with the incorporated comments as recorded on RCR's and meeting minutes.
Date:
November 4, 1998
Creator:
Adams, M. R.
Object Type:
Report
System:
The UNT Digital Library
Tank waste remediation system process engineering instruction manual
The purpose of the Tank Waste Remediation System (TWRS) Process Engineering Instruction Manual is to provide guidance and direction to TWRS Process Engineering staff regarding conduct of business. The objective is to establish a disciplined and consistent approach to business such that the work processes within TWRS Process Engineering are safe, high quality, disciplined, efficient, and consistent with Lockheed Martin Hanford Corporation Policies and Procedures. The sections within this manual are of two types: for compliance and for guidance. For compliance sections are intended to be followed per-the-letter until such time as they are formally changed per Section 2.0 of this manual. For guidance sections are intended to be used by the staff for guidance in the conduct of work where technical judgment and discernment are required. The guidance sections shall also be changed per Section 2.0 of this manual. The required header for each manual section is illustrated in Section 2.0, Manual Change Control procedure. It is intended that this manual be used as a training and indoctrination resource for employees of the TWRS Process Engineering organization. The manual shall be required reading for all TWRS Process Engineering staff, matrixed, and subcontracted employees.
Date:
November 4, 1998
Creator:
Adams, M. R.
Object Type:
Report
System:
The UNT Digital Library
FY98 final report for the expedited technology demonstration project: demonstration test results for the integrated MSO waste treatment system
Molten Salt Oxidation (MSO) is a promising alternative to incineration for the treatment of a variety of organic wastes. Lawrence Livermore National Laboratory (LLNL) has prepared a facility in which an integrated pilot-scale MSO treatment system is being tested and demonstrated. The system consists of a MSO vessel with a dedicated off-gas treatment system, a salt recycle system, feed preparation equipment, and a ceramic final waste forms immobilization system. This integrated system was designed and engineered based on operational experience with an engineering-scale reactor unit and extensive laboratory development on salt recycle and final forms preparation. The MSO/off-gas system has been operational since December 1997. The salt recycle system and the ceramic final forms immobilization became operational in May and August, 1998, respectively. We have tested the MSO facility with various organic feeds, including chlorinated solvents, tributyl phosphate/kerosene, PCB-contaminated waste oils & solvents, booties, plastic pellets, ion exchanged resins, activated carbon, radioactive-spiked organics, and well-characterized low-level liquid mixed wastes. MSO is shown to be a versatile technology for hazardous waste treatment and may be a solution to many waste disposal problems in DOE sites. This report presents the results obtained from operation of the integrated pilot-scale MSO treatment system through …
Date:
November 1, 1998
Creator:
Adamson, M G; Hipple, D L; Hopper, R W & Hsu, P C
Object Type:
Report
System:
The UNT Digital Library
New Neutron Rich Nuclei Near {sup 208}Pb
The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as …
Date:
November 13, 1998
Creator:
Aeystoe, J.; Andreyev, A.; Evensen, A.-H.; Hoff, P.; Huhta, M.; Huyse, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Uncertainty and approximate reasoning in waste pretreatment planning
Waste pretreatment process planning within the DOE complex must consider many different outcomes in order to perform the tradeoffs necessary to accomplish this important national mission. One of the difficulties encountered by many who assess these tradeoffs is that the complexity of this problem taxes the abilities of any single person or small group of individuals. For example, uncertainties in waste composition as well as process efficiency are well known yet incompletely considered in the search for optimum solutions. This paper describes a tool, the pre-treatment Process Analysis Tool (PAT), for evaluating tank waste pretreatment options at Hanford, Oak Ridge, Idaho National Environmental and Engineering Laboratory, and Savannah River Sites. The PAT propagates uncertainty in both tank waste composition and process partitioning into a set of ten outcomes. These outcomes are, for example, total cost, Cs-137 in iLAW, iHLW MT, and so on. Tradeoffs among outcomes are evaluated or scored by means of an approximate reasoning module that uses linguistic bases to evaluate tradeoffs for each process based on user valuations of outcomes.
Date:
November 1, 1998
Creator:
Agnew, S.F.; Eisenhawer, S.W. & Bott, T.F.
Object Type:
Report
System:
The UNT Digital Library
Report to users of ATLAS - September 1998.
The ATLAS facility has provided a total of 5749 hours of beam for research in FY1998. The accelerator operation had a very high 93% reliability factor during that period. With the startup of Gammasphere in January, our schedule has attempted to minimize scheduled downtime and maximize beam-time for research. Our best performance so far occurred during the month of May when a total of 639 hours was provided for research. From the accelerator point-of-view, recent major highlights have included first operation of a new production configuration for our {sup 17}F beams which increased the beam current on-target to 2 x 10{sup 6} {sup 17}F ions/see. The {sup 17}F production target was moved approximately 4 meters upstream and a new superconducting solenoid was added to the system to refocus the highly divergent secondary beam. This new location also places the target upstream of a new superconducting resonator which was used to reduce the energy spread of the beam delivered to the spectrograph to less than 300 keV (FWHM). An improved, liquid nitrogen cooled, multiple gas cell has also significantly contributed to better performance.
Date:
November 18, 1998
Creator:
Ahmad, I. & Hofman, D.
Object Type:
Report
System:
The UNT Digital Library
Reciprocal-Space Analysis of Compositional Modulation in Short-Period Superlattices Using Position-Sensitive X-Ray Detection
Epitaxial growth of AlAs-InAs short-period superlattices on (001) InP can lead to heterostructures exhibiting strong, quasi-periodic, lateral modulation of the alloy composition; transverse satellites arise in reciprocal space as a signature of the compositional modulation. Using an x-ray diffractometer equipped with a position-sensitive x-ray detector, we demonstrate reciprocal-space mapping of these satellites as an efficient, nondestructive means for detecting and characterizing the occurrence of compositional modulation. Systematic variations in the compositional modulation due to the structural design and the growth conditions of the short-period superlattice are characterized by routine mapping of the lateral satellites. Spontaneous compositional modulation occurs along the growth front during molecular-beam epitaxy of (AlAs) (InAs)n short-period superlattices. The modulation is quasi-periodic and forms a lateral superlattice superimposed on the intended SPS structure. Corresponding transverse satellites arise about each reciprocal lattice point, and x-ray diffraction can be routinely used to map their local reciprocal-space structure. The integrated intensity, spacing, orientation, and shape of these satellites provide a reliable means for nondestructively detecting and characterizing the compositional modulation in short-period superlattices. The analytical efficiency afforded by the use of a PSD has enabled detailed study of systematic vacations in compositional modulation as a function of the average composition, the …
Date:
November 10, 1998
Creator:
Ahrenkiel, S. P.; Follstaedt, D. M.; Lee, S. R.; Millunchick, J. M.; Norman, A. G.; Reno, J. L. et al.
Object Type:
Article
System:
The UNT Digital Library
Proton Radioactivity Measurements at HRIBF: Ho, Lu, and Tm Isotopes
Two new isotopes, {sup 145}Tm and {sup 140}Ho and three isomers in previously known isotopes, {sup 141m}Ho, {sup 150m}Lu and {sup 151m}Lu have been discovered and studied via their decay by proton emission. These proton emitters were produced at the Holifield Radioactive Ion Beam Facility (HRIBF) by heavy-ion fusion-evaporation reactions, separated in A/Q with a recoil mass spectrometer (RMS), and detected in a double-sided silicon strip detector (DSSD). The decay energy and half-life was measured for each new emitter. An analysis in terms of a spherical shell model is applied to the Tm and Lu nuclei, but Ho is considerably deformed and requires a collective model interpretation.
Date:
November 13, 1998
Creator:
Akovali, Y.; Batchelder, J. C.; Bingham, C. R.; Davinson, T.; Ginter, T. N.; Gross, C. J. et al.
Object Type:
Article
System:
The UNT Digital Library
Quarterly Technical Progress Report - Investigation of Syngas Interaction in Alcohol Synthesis Catalysts
This report presents the work done on " Investigation of Syngas Interaction in Alcohol Synthesis Catalysts" during the last quarter. The major activity during this period is on FTIR absorption studies of Co/Cr catalysts using CO as a probe molecule. Transition metals cobalt and copper play significant roles in the conversion of syngas (CO + H2 ) to liquid fuels. With a view to examine the nature of interaction between CO and metal, the FTIR spectra of CO adsorbed on Co-Cr2 O3 composites were investigated. The results indicate that as cobalt loading increases, the intensity of the CO adsorption bands increase and several vibrational modes seem to be promoted. Heat treatment of the sample revealed two distinct processes of adsorption. Bands due to physisorption disappeared while bands due to chemisorption not only increased in intensity but persisted even after desorption. It seems that the physisorption process is more active when the catalyst is fresh and is hindered when carbidic/carbonyl formations occur on the metal surfaces.
Date:
November 10, 1998
Creator:
Akundi, Murty A.
Object Type:
Report
System:
The UNT Digital Library
Composition and Bonding in Amorphous Carbon Films Grown by Ion Beam Assisted Deposition: Influence of the Assistance Voltage
Amorphous carbon films have been grown by evaporation of graphite with concurrent Ar+ ions bombardment assistance. The ion energy has been varied between 0-800 V while keeping a constant ion to carbon atom arrival ratio. Film composition and density were determined by ion scattering techniques (RBS and ERDA), indicating a negligible hydrogen content and a density dependence with the assistance voltage. The bonding structure of the films has been studied by Raman and X-ray Absorption Near-Edge (XANES) spectroscopy. Different qualitative effects have been found depending on the ion energy range. For ion energies below 300 eV, there is a densification of the carbon layer due to the increase in the sp3 content. For ion energies above 300 eV sputtering phenomena dominate over densification, and thinner films are found with increasing assistance voltage until no film is grown over 600 V. The films with the highest SP3 content are grown with intermediate energies between 200-300 V.
Date:
November 12, 1998
Creator:
Albella, J. M.; Banks, J. C.; Climent-Font, A.; Doyle, B. L.; Gago, R.; Jimenez, I. et al.
Object Type:
Article
System:
The UNT Digital Library
Elastic Wave Radiation from a Line Source of Finite Length
Straightforward algebraic expressions describing the elastic wavefield produced by a line source of finite length are derived in circular cylindrical coordinates. The surrounding elastic medium is assumed to be both homogeneous and isotropic, anc[ the source stress distribution is considered axisymmetic. The time- and space-domain formulae are accurate at all distances and directions from the source; no fa-field or long-wavelength assumptions are adopted for the derivation. The mathematics yield a unified treatment of three different types of sources: an axial torque, an axial force, and a radial pressure. The torque source radiates only azirnuthally polarized shear waves, whereas force and pressure sources generate simultaneous compressional and shear radiation polarized in planes containing the line source. The formulae reduce to more familiar expressions in the two limiting cases where the length of the line source approaches zero and infinity. Far-field approximations to the exact equations indicate that waves radiated parallel to the line source axI.s are attenuated relative to those radiated normal to the axis. The attenuation is more severe for higher I?equencies and for lower wavespeeds. Hence, shear waves are affected more than compressional waves. This fi-equency- and directiondependent attenuation is characterized by an extremely simple mathematical formula, and is …
Date:
November 4, 1998
Creator:
Aldridge, D.F.
Object Type:
Report
System:
The UNT Digital Library